The invention concerns a load torque lock for automatically locking load-side torques.
Load torque locks belong to the species of automatically locking locks and are used in terms of their functioning with self-switching free-wheel mechanisms. They are installed as locking elements in a drive train and automatically block the torques initiated by the output mechanism in one or both directions of rotation when the driving mechanism is at an standstill, while the torques initiated by the drive side are transmitted in the one or the other direction of rotation. As a result, torques acting on the load side in a drive train can be supported and locked with the aid of the load torque lock against a stationary frame or housing. It forms a safety element, which prevents impermissible movement of the load side from outside forces or torques in the case of a decrease or cessation of the driving mechanism. Such load torque locks are suited especially for use in drive trains with alternating directions of rotation. Using them permits braking systems or self-locking transmissions that would otherwise be required to be dispensed with.
Different types of physical effects are already currently being utilized for load torque locks. Thus, in accordance with DE 30 30 767 C2, a coil spring lock is used for manually driven lifting apparatuses, which utilize a frictionally engaged catch band effect. Moreover, the utilization of a frictional clamping effect is known in accordance with G 89 10 857, according to which clamping rollers cooperate with a profiled output shaft.
These systems are based on frictionally engaged principles of action and require a certain pretension of the clamping or locking elements for continual locking readiness in order to cooperate quickly and reliably with components fixed to a frame with the occurrence of load torques. As a result of this pretension of the clamping or locking elements, which is not completely suspended even in the case of a drive-side drive-through, they remain in continual frictional contact with the components fixed to a frame. However, this results in high frictional losses and poor efficiency, which leads to greater warming when high rpms are to be transmitted. The range of application of the load torque locks functioning according to the known frictionally engaged principles of action is therefore restricted to driving mechanisms with low rpms.
Another design of the load torque locks is known from DE 197 53 106 C2, which is based on the tilting and swiveling effect. The clamping or locking bodies used there are carried along by rotating the drive shaft with driving elements on an orbit, which has a relatively large radial distance to the axis of rotation of the load torque lock. Because of this off-center arrangement of the clamping or locking bodies, centrifugal forces develop in the case of a drive-side drive-though, which can for their part cause undesired tilting of the clamping or locking bodies. In fact the patent specification mentions in reference to FIG. 9 that in order to avoid frictional contact of the clamping or locking bodies with the clamping or locking ring unit that is fixed to a frame from developing centrifugal forces, these centrifugal forces can be supported by a certain embodiment via the add-on parts of the output shaft. However, this is only the case at a certain operating point dependent upon the driving mechanism's rpms and the torque.
The attainment at hand attempts to embody a load torque lock in such a way that an impermissible response of the load torque lock to centrifugal forces is reliably avoided over the entire rpm range.